Blizzard has released the results of the third beta survey, and published the results with commentary by Dustin Browder that discusses some plans for future patches:

We've recently compiled the results of the third beta survey and wanted to share the numbers with you. Over 60,000 survey results were collected from around the globe from those in the StarCraft II beta. Keep in mind that the questions and results were presented and collected before beta patch 9, so the results don't take into account any changes players saw with that or subsequent patches.

It is no surprise that the Marauder is every Terran player’s favorite. They are hard to kill and pack quite a punch. We are surprised to see Hellion towards the bottom of the list since we are seeing so many games where they just destroy light targets. Still, we are going to make some changes in the next patch to make Hellions a little easier to use.My favorite new Protoss unit is:Colossus 27.6%Immortal 19.4%Stalker 13.3%Sentry 11.8%Mothership 10.5%Void Ray 10.2%Warp Prism 4.2%Phoenix 2.9%

Again the big hitters are at the top of the list, with Colossus and Immortal leading the lists in popularity. Both very vulnerable to air attacks but with Stalkers coming up third Protoss player’s obviously feel like they can protect their heavy robotic units. We are going to be making some changes in the next patch to Phoenix to make him a little easier to use and a little more powerful.